Before the end of the Palæozoic Period the Conifers had appeared, descended possibly from the extinct _Cordaiteæ_. With the advent of the Secondary or Mesozoic epoch the group of the Cycads, to which our modern Screw-pines belong, rose to great importance, descended probably from the Pteridosperms, and long continued to be a dominant feature of terrestrial vegetation. And then at last in the Lower Cretaceous rocks the Angiosperms, or “Flowering Plants” _par excellence_, both Dicotyledons and Monocotyledons, put in an appearance. It seems probable that they were evolved from Cycads, such as the _Bennettiteæ_, recent researches on magnificent fossil material discovered in America showing striking analogies between certain Cycadaceous flowers and those of such plants as Magnolias, Water Lilies, and Buttercups. Once established, the Angiosperms rose to primary importance in an extraordinarily short time--very possibly owing to the “invention” of insect pollination, which may have arisen at that period. In Upper Cretaceous times the two great groups into which the Angiosperms still fall, the Dicotyledons and Monocotyledons, fairly dominated the flora of the world, as they do at present. Already many types familiar at the present day had appeared, and the woods were filled with Birches, Beeches, Oaks, Planes, Maples, Hollies, Ivies, as they are nowadays. The record of the rocks during these long periods of time contains not only the story of the rise of the great divisions of the vegetable world, but also of the decline of most of them. A few, like the Pteridosperms and the Sphenophylls, died out completely long ago; but most of the great groups of early days, such as Cycads, Ferns, Horsetails, and Club-mosses, still survive, though shorn of much of their glory. [Illustration: FIG. 27.--LEAF OF MAIDENHAIR TREE (GINKGO BILOBA). 2/3.]